About the same time that President Bush was condemning the abuse of prisoners in Iraq as un-American, a year-long inquiry began into the mistreatment of prisoners at home.

The most secure prisons in the US are the notorious Supermaxes

The Commission on Safety and Abuse in America's Prisons (CSAAP) issues its final report in about eight weeks time, but the testimony of violence, abuse and over-crowding it has already heard has shocked few familiar with the largest documented prison system in the world.

More than 2.1 million people are in jail in the US at any one time; that is about one in 140 Americans, or as many people as live in Namibia, or nearly five Luxembourgs - and it is a number that continues to rise.

One of the biggest drivers of the expanding population are the tough policies brought in over the last 20 years to tackle high crime rates - like the "three strikes" laws that hand out long, mandatory sentences to repeat offenders.

They are tactics the US government says are working - as recent figures have shown violent crime and murder falling.

But critics say that such policies have skewed the US system away from rehabilitation, storing up problems for the future.

End of the road

The most secure prisons in the US are the notorious Supermax facilities, like the correctional complex in Florence, Colorado that houses shoe bomber Richard Reid, and which is also known as the Alcatraz of the Rockies.

USP Florence is known as the Alcatraz of the Rockies

Tightly controlled, technologically advanced and utterly dispiriting, such facilities - and smaller blocks within general prisons - have been a source of controversy for many years.

Bland, bureaucratic phrases like management control or secured housing unit describe regimes where solitary confinement is an almost permanent way of life, with prisoners locked in spartan cells for at least 23 hours each day.

Unfortunately, new prisons are being built to minimize the number of staff, both in architectural design and by using technologies such as remote cameras and sensor systems

Gary HarkinsPrison officer

Built in 1994 at a cost of about $60m, the Supermax in Florence is said to be equipped with 1,400 remote-controlled steel doors, motion detectors, pressure pads and gun towers with perfect sightlines across the complex.

Supermaxes are the end of the road for those in the prison system - transfer to an even marginally less restrictive environment can require several years of good behaviour.

To supporters they are the most appropriate way to house the worst of the worst in the prison population, especially those criminals who attacked or killed guards and other prisoners.

To critics, they are a breeding ground for monsters, an affront to human rights tantamount to torture.

'Dehumanizing'

Gary Harkins, is an officer at the maximum security Oregon State Penitentiary in Salem, and also a member of Corrections USA, a group which represents about 120,000 prison guards and opposes the growing number of private prisons.

"Get tough" sentencing has increased the US prison population

Mr Harkins says OSP works on a "direct supervision" basis, encouraging officers to have interpersonal contact with inmates.

This, he says, reduces the threat of violence and makes for a safer institution for both inmates and staff, who are armed with only a radio, a whistle, and a pair of handcuffs.

He told the CSAAP inquiry: "Unfortunately, new prisons are being built to minimize the number of staff, both in architectural design and by using technologies such as remote cameras and sensor systems.

"This dehumanizes the inmates and staff alike.

"I also believe that you need to take the effort of actually walking among the inmates and engaging them in conversation.

People believe there is nothing they can do about it, they don't pay any attention to the consequences the treatment of prisoners has when they come out, and they don't participate in the debate

"Unfortunately, with the drastic cutbacks in educational and vocational programs we are currently experiencing, this is becoming a harder task."

Prisons in the US are run on federal, state and local levels.

The US Department of Justice says it "protects society by confining offenders in the controlled environments of prisons and community-based facilities that are safe, humane, cost-efficient, and appropriately secure".

"Each federal prison provides services to help prepare inmates to return to their communities as productive citizens," it adds in a statement on its website.

Examples include educational, occupational and vocational training, work programmes and substance abuse treatment.

Roots of problem

America currently stands accused of acting as the world's jailer in its War on Terror. It is under fire for allegedly running secret jails in other countries, far from public scrutiny.

From Guantanamo Bay in Cuba, to Abu Ghraib in Iraq and Bagram airbase in Afghanistan, activists say the US is trampling on human rights in its pursuit of terror suspects.

But the roots of the problem may be closer to home, as suggested by words attributed to former Pennsylvania prison guard Charles Graner - ringleader of the Abu Ghraib abuses - which came out during court testimony.

"The Christian in me says it's wrong, but the corrections officer in me says, 'I love to make a grown man piss himself.'"

No one would suggest Graner represents of the vast majority of prison officers.

But Alexander Busansky, executive director of the CSAAP, told the BBC the US public was largely ignorant of the real state of America's prisons.

"We have to get away from the idea that what happens in prisons stays in prisons. Prisons are public institutions and they must be held accountable."

He said the CSAAP would be recommending expansion of the prison accreditation scheme, increased use of direct supervision in jails and tighter regulation over the use of weapons like pepper spray and stun guns in a bid to end abuses.

"There has been a hardening of attitudes," Mr Busansky said.

"People believe there is nothing they can do about it, they don't pay any attention to the consequences the treatment of prisoners has when they come out, and they don't participate in the debate.

"But prison is a place of opportunity, and it can have a positive impact on people's lives."